Speed prexy Hunter Nickell has resigned his post at the network, effective at the end of the year.

Nickell has topped Speed since 2005, coming there after 12 years as FSN South g.m. He plans to consult on a number remaining key Speed projects over the next few months while exploring new opportunities in Fox Sports Media Group.

A Speed spokesman said an interim replacement should be named by week’s end for Nickell, whose decision to depart appears to have come relatively suddenly.

“It’s unfortunate that Hunter is stepping away after all that he’s done for Speed,” Fox Sports Media Group chairman David Hill said. “He’s a man of great character, a true gentleman and he’s served Fox tirelessly for many years.”

Speed’s reach grew by nearly 25% to 84 million homes under Nickell’s tenure, thanks in part to new high-profile events including the NASCAR Sprint All-Star Race, the NASCAR Hall of Fame Induction ceremonies and all three of the NASCAR post-season awards banquets. Nickell has also been credited with better marketing Speed at NASCAR events and building relationships with other major race orgs.

“I worked with great people and awesome partners,” Nickell said. “I am grateful, and I have had a blast.”